ignore echo messages from facebook

[aristidednd]

According to Facebook Messenger API documentation https://developers.facebook.com/docs/messenger-platform/reference/webhook-events/message-echoes/?locale=en_En, an echo message is also triggered for image, video, file, and audio attachments.
These changes ignore those echo messages.

Proposed changes:

• Ignore echo messages related to file, audio, video, and image attachments from Facebook

Status (please check what you already did):

• added some tests for the functionality
• updated the documentation
• updated the changelog (please check changelog for instructions)
• reformat files using black (please check Readme for instructions)

[CLAassistant]

All committers have signed the CLA.

[stale]

This PR has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ancalita]

@aristidednd Thank you for your contribution! 💯
Could you please add a changelog entry specifying the why and how of your improvement.
Also if possible please add unit test coverage.

[ancalita]

I think adding this in the different _is_<type>_message checks leads to these methods having more than 1 purpose. I suggest instead extracting this boolean variable in a separate function _is_echo_message and then adding this check once only at the top of the message method before all the other checks:

    async def message(
        self, message: Dict[Text, Any], metadata: Optional[Dict[Text, Any]]
    ) -> None:
        """Handle an incoming event from the fb webhook."""
        if self._is_echo_message(message):
                logger.warning("Received a message echo from Facebook which will be ignored.")
                return None
        # quick reply and user message both share 'text' attribute
        # so quick reply should be checked first
        if self._is_quick_reply_message(message):
              ...

[Tung8787]

Tui chả hiểu hì :)))